fuel tank sending unit - The 1947 - Present Chevrolet & GMC Truck Message Board Network

JayE72 · 09-25-2010, 10:56 AM

Greetings everyone! Thank you in advance for your help and insight. I'm having a problem with my gas gauge on my 1972 Cheyenne 350, SB, A/T. I was reading several post related to this matter and noticed that I should have a ground wire attached some where to the sending unit or fuel tank. Can anyone help me with a picture of what and where the ground should be attached to? Thank you.

68gmsee · 09-25-2010, 11:55 AM

If you are referring to a ground strap, there's none used on the tank or sending unit. The tank itself is self grounded to the frame with the bottom bolts.

What sort of problems are you having? I'll look for the info on how to check it and post it shortly -unless someone has it readily available.

68gmsee · 09-25-2010, 12:01 PM

Hrere is the site.

http://www.6066gmcguy.org/Electrical-02.htm

**Classic Heartbeat** · 09-25-2010, 12:12 PM

The tank does not have a ground strap. It is grounded to the cab through the mounting bolts. You need to expain the simptoms so we can help you figure out your problem. If you want to find out if your sending unit is working, then you need to pull it and hook it up to an ohm meter. If it reads "0"ohms at its lowest point and "90" at it highest, then the sending unit is not the problem. While it is out you will be able to check the float to make sure it is not full of gas. You just work your way back to the gauge from there. WES

cdowns · 09-25-2010, 12:51 PM

tho the tank is supposed to ground with the mounting bolts(so is the rear bed HAHAHA) i've run ground wires to the body as a backup to make completely negative that i have solid grounds in place

the only time its bad to run a groud is if you're in a boat

JayE72 · 09-25-2010, 02:46 PM

The gauge is pegged past full. The owner that had the truck before me had removed the wire to the sending unit. I got a new one (wire) and hooked it up. The gauge moved closer to the F line but it is still out of the range of the gauge. I tried to ground the gauge about 8 months ago it went to E but I burned an electrical run on the board. I repaired the burned piece. I have a backup gauge cluster perhaps this will work?

JayE

De Fuego · 09-25-2010, 06:46 PM

I have the same issue. My needle was pegged way past the F.. I found a loose ground wire. This fixed it and the gas gauge worked temporarily. Now all of a sudden its stuck past the F again...Sorry. No help here

Zoomin · 09-25-2010, 11:05 PM

The is a brown (tan) wire that runs from the tank to the wiring harness in the fuse block, which in turn goes to the fuel gauge via the instrument panel harness, then to the printed circuit, and finally to the gauge. NOTE - this wire is not supposed to be connected to a power source!

The sending unit acts as a rheostat, causing the needle on the gauge to register how much current is being allowed to pass through. When the needle is pegged past full, that means your brown wire isn't conducting between your sending unit and gauge. You could have a bad printed circuit in the back of the gauge panel.

JayE72 · 09-26-2010, 01:01 AM

Thank you Zoomin. When I bought the truck the needle was already pegged. The wire was missing. I put a new wire on the sending unit and it didn't change much. It went from way past F to close to F.

Thanks Classic Heartbeat. Do you carry the fuel sending unit on your website?

Thanks to 68gmsee.

Thanks to all that responded to the thread!

09-25-2010, 10:56 AM	#1
JayE72 Registered User Join Date: May 2009 Location: Greensboro NC Posts: 40	fuel tank sending unit Greetings everyone! Thank you in advance for your help and insight. I'm having a problem with my gas gauge on my 1972 Cheyenne 350, SB, A/T. I was reading several post related to this matter and noticed that I should have a ground wire attached some where to the sending unit or fuel tank. Can anyone help me with a picture of what and where the ground should be attached to? Thank you.

09-25-2010, 11:55 AM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: fuel tank sending unit If you are referring to a ground strap, there's none used on the tank or sending unit. The tank itself is self grounded to the frame with the bottom bolts. What sort of problems are you having? I'll look for the info on how to check it and post it shortly -unless someone has it readily available.

09-25-2010, 12:01 PM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: fuel tank sending unit Hrere is the site. http://www.6066gmcguy.org/Electrical-02.htm

09-25-2010, 12:12 PM	#4
Classic Heartbeat Project Junkie! Fishing Poor!! Join Date: Dec 1999 Location: Olympia,Wa. 98512 Posts: 10,770	Re: fuel tank sending unit The tank does not have a ground strap. It is grounded to the cab through the mounting bolts. You need to expain the simptoms so we can help you figure out your problem. If you want to find out if your sending unit is working, then you need to pull it and hook it up to an ohm meter. If it reads "0"ohms at its lowest point and "90" at it highest, then the sending unit is not the problem. While it is out you will be able to check the float to make sure it is not full of gas. You just work your way back to the gauge from there. WES __________________ On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys

09-25-2010, 12:51 PM	#5
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: fuel tank sending unit tho the tank is supposed to ground with the mounting bolts(so is the rear bed HAHAHA) i've run ground wires to the body as a backup to make completely negative that i have solid grounds in place the only time its bad to run a groud is if you're in a boat __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

09-25-2010, 02:46 PM	#6
JayE72 Registered User Join Date: May 2009 Location: Greensboro NC Posts: 40	Re: fuel tank sending unit The gauge is pegged past full. The owner that had the truck before me had removed the wire to the sending unit. I got a new one (wire) and hooked it up. The gauge moved closer to the F line but it is still out of the range of the gauge. I tried to ground the gauge about 8 months ago it went to E but I burned an electrical run on the board. I repaired the burned piece. I have a backup gauge cluster perhaps this will work? JayE

09-25-2010, 06:46 PM	#7
De Fuego Registered User Join Date: Jul 2010 Location: Portales, NM Posts: 27	Re: fuel tank sending unit I have the same issue. My needle was pegged way past the F.. I found a loose ground wire. This fixed it and the gas gauge worked temporarily. Now all of a sudden its stuck past the F again...Sorry. No help here __________________ Last edited by De Fuego; 09-25-2010 at 06:47 PM.

09-25-2010, 11:05 PM	#8
Zoomin Man of Mini-Talents Join Date: Sep 2009 Location: Oklahoma City, OK Posts: 4,295	Re: fuel tank sending unit The is a brown (tan) wire that runs from the tank to the wiring harness in the fuse block, which in turn goes to the fuel gauge via the instrument panel harness, then to the printed circuit, and finally to the gauge. NOTE - this wire is not supposed to be connected to a power source! The sending unit acts as a rheostat, causing the needle on the gauge to register how much current is being allowed to pass through. When the needle is pegged past full, that means your brown wire isn't conducting between your sending unit and gauge. You could have a bad printed circuit in the back of the gauge panel. __________________ Steve Project - Ruth 66 Skylark Project - Lola 60 Biscayne Project - Iron Ox 54 GMC 100 Project - Darth 69 Camaro Last edited by Zoomin; 09-25-2010 at 11:06 PM.

09-26-2010, 01:01 AM	#9
JayE72 Registered User Join Date: May 2009 Location: Greensboro NC Posts: 40	Re: fuel tank sending unit Thank you Zoomin. When I bought the truck the needle was already pegged. The wire was missing. I put a new wire on the sending unit and it didn't change much. It went from way past F to close to F. Thanks Classic Heartbeat. Do you carry the fuel sending unit on your website? Thanks to 68gmsee. Thanks to all that responded to the thread!



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